macOS Desktop app: slash commands only recognized at the very start of a message, and only once per session

Environment

• Claude Code Desktop app (macOS)
• Version: 1.37937.1
• Fully quit-and-relaunched the app and rebooted macOS — issue persists, ruling out local cache/session corruption.

Bug
Slash commands (built-in and custom skill-based ones) are only recognized when typed at the very beginning of a message. A slash command typed anywhere else in a message, or a second slash command in a later message in the same session, is not recognized/invoked.

Steps to reproduce

1. Open Claude Code Desktop app on macOS.
2. Send a message starting with a slash command (e.g. /help or a custom skill command) — works as expected.
3. In a later message, try to invoke another slash command — it fails / is treated as plain text ("Unknown slash command" or simply not triggered).

Expected behavior
Slash commands should be recognized anywhere a / command is typed, and repeatedly within a session, matching behavior in the terminal CLI (claude), which does not have this restriction.

Related
This appears to be a long-standing issue, not new: #15301 (Dec 2025) and #44488 (Apr 2026) report the same core symptom and were both closed as duplicates, but I cannot find the tracking issue they were merged into, and the behavior is still present on the current version as of August 2026.